1. IP Business Trunking services in the US are mainly provided by CLECs. The traffic mix generated by large enterprises is huge and varied: something a CLEC is not capable of handling. Large enterprise users have shown preference to work with the likes of Global Crossing and Level 3 for traffic termination (which can be classified as a subset of IP business trunking service).

2. Quality of service offered by IP Business Trunking providers has not reached the requisite level of quality

3. In order to subscribe to IP Business Trunking service, most of the large enterprises have to migrate from TDM to IP. This they cannot be bothered to work out especially since they are already using TDM business trunking.

4. Large enterprises have fair amount of international long distance traffic, which is not being provided over managed networks by most of the IP Business Trunking service providers.

5. IP Business Trunking tends to be associated with hosted VoIP. At least that is how the service providers usually market it. Hosted VoIP has never been popular among the large enterprises.